Pyrolysis of a liquid hydrocarbon material is a well-known process that involves heating the material to a temperature that is high enough to cause thermal decomposition of larger molecules to form smaller molecules. Pyrolysis may be accomplished with a diluent, such as steam, to produce more favorable product distribution. A pyrolysis process produces a highly unsaturated and very unstable product, hereinafter called the effluent from the pyrolysis process, or simply the effluent.
The effluent is usually rich in olefins, diolefins, acetylenes and other highly unstable compounds, and there is a strong tendency for these materials to react to form high molecular weight products which may be identified collectively as coke or tar. Such products are not desirable and to avoid forming them it is essential to reduce the temperature of the effluent quickly to a stable temperature, that is, to a temperature that is so low that rapid reactions of unstable compounds with each other do not take place.
My copending application, U.S. Ser. No. 106,291, filed even date herewith, describing an invention entitled Quench Process, and which disclosure is incorporated herein by reference, describes an efficient process for recovering heat, particularly as high grade steam. That process has the advantage that inexpensive quench liquids, such as pitch, fractionator bottoms, etc., may be employed as quench liquid. However, because such materials may contain coke and high molecular products which might tend to form coke, and because the pyrolysis effluent does contain such materials, it may be desirable to provide a method to prevent buildup of such materials in the quench system. The invention provides such a method.